Over the last half-century or so, English has risen to become the dominant global language of the era, spoken as the default in everything from international business transactions to air travel. But achieving a global reach doesn’t necessarily give a language long-term staying power, as the Assyrians and the Silk Road traders found out centuries ago. Then again, some languages are kept alive past their political and economic prime by a powerful religious influence. Linguist Nicholas Ostler’s new book delves into all of these factors, and aims to sort out what gives a language its power, and what can take that power away in a heartbeat.